Table 4.

Overview of main non-chemical treatments.

Treatment	Mode of action	+	–	P/C	Comm.	References
Plant-derived products	Acaricidal, toxic	Short environmental persistence	Short effect	C	X	(74–76)
	Repellent	Potential in attract-and-kill	Lack of standardization	P	X	(77)
Vaccines	Boost immunity	-Low risk for resistance -No workload during production	Further research needed for commercialization	P		(78)
Biological control
Predatory mites	Prey on PRM	No negative effect on environment (natural enemies)	Also affected by other treatments (silica, acaricides,.)	P(/C)	X	(79, 80)
Entomopathogenic fungi	Penetrate host	Potential in traps	Suboptimal conditions in layer houses	C	X	(81)
Nematodes + endosymbionts			Much research still needed			(82, 83)
Physical control
Inert dusts (on system)	Dessication of PRM	-Resistance less likely (mainly physical mode of action)	-Health hazards (esp. crystalline) -Variability in effectiveness	P/C	X	(84, 85)
Q perch	Electrify PRM	-No harm to hens-Resistance less likely	Expensive, change in infrastructure	P	X	(62)

Treatments non-allowed in EU (light regime, oils) are not included. Main advantages (+) and disadvantages (–) are listed, as well as their use (P, preventively; C, curatively) and whether they are commercially available (Comm.). For each treatment, main references are given. For further details and other references: see text.